title: Active extrusion of Ca2+ from epiphysial chondrocytes of normal and rachitic chickens.
abstract: Chondrocytes isolated from the epiphysial cartilage of chickens were exposed to either the ionophore A23187 or KCN, in the presence of 0.4 mM-extracellular Ca2+. This treatment elicits a prompt release of cell Ca2+, which can be measured as net cation efflux by a highly sensitive Ca2+-selective electrode system. Pre-exposure of chondrocytes to the metabolic inhibitors 2-deoxy-D-glucose or oligomycin causes a parallel decrease in both cell ATP and ionophore-mediated Ca2+ extrusion. Conversely, substitution of extracellular Na+ with choline produces only a very small decrease in the rate of Ca2+ efflux. This indicates that the ionophore A23187 and cyanide induce the mobilization of intracellular Ca2+, which is then extruded from the cell mainly by an ATP-driven pump system. Chondrocytes isolated from the cartilage of rachitic chickens also exhibit the capacity for extruding Ca2+ by the same mechanism, with an efficiency comparable with that of their normal counterpart.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002356:Cartilage / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D002645:Chickens; D066298:In Vitro Techniques; D011190:Potassium Cyanide / Q000494:pharmacology; D012279:Rickets / Q000378:metabolism*
chemical_list: D000001:Calcimycin; D000255:Adenosine Triphosphate; D011190:Potassium Cyanide; D002118:Calcium